Automatic variator assembly for varying the valve timing

Abstract: An automatic variator for use in an internal combustion engine and other engines which use valve-type distribution systems, to operate a twin set of double-effect distribution sequential valve shafts for the purpose of regulating the valve overlap or timing and the valve opening section or to operate a double overhead camshaft with poppet valves for the purpose of regulating valve overlap or timing while the engine is running. A motor reducer advances (42) a spindle (44) against the valve shaft with a grooved screw (41) at one end of the same, causing the shaft to turn and move, thereby varying the valve overlap or the valve section and valve overlap.

Description: FIELD OF THE INVENTION The present invention relates to an automatic variator assembly for varying the valve timing in a valvular distribution system in an internal combustion engine which includes an engine block, a cylinder formed in the engine block, the cylinder having a cylinder head, a piston slidable within the cylinder, and a combustion chamber bounded by the cylinder and the piston, and a distribution system consisting of two camshafts with valves located in the cylinder head, the variator assembly comprising an automatic mechanism; a spindle for moving one of said camshafts, a motor activated by said automatic mechanism which causes an end of said spindle to advance and push the camshaft forward or pull it back and a threaded sleeve as known from WO-A-82/02742. BACKGROUND OF THE INVENTION The function of valves in internal combustion engines is related to the precise timing of the opening of the intake valve in relation to the opening of the exhaust valve at given points in the location of the piston, be it at the bottom or at the top of the cylinder. To permit the outflow of gases the exhaust valve begins to open at the end of the third stroke and remains open during the entire fourth stroke, at which point the intake valve begins to open before the first stroke. The instant during which both valves are open is designated "overlap" or "timing" in this description. In the systems of the prior art, based on twin or dual overhead camshafts, in order to vary the overlap or timing of an intake valve in respect to an exhaust valve, it is necessary to change, the angular placement (in a vertical plane) of one of the camshafts with respect to the other. Once the change is accomplished the new valve overlap remains fixed. There are known devices for changing the overlap or timing through rotation of camshafts while the engine is in operation. However, such devices are very sophisticated and are currently applied only in high-performance engines. A variator of the present invention produces the desired rotation of a conventional camshaft, as more fully described below. A double effect distribution sequential valve shaft system ("SVS") also performs the same rotation while also being capable of modifying the opening section, as more fully described below, to enlarge or reduce the space through which the gases will flow in the distribution system. In the prior art, the enlargement of valve area occurs only by depressing the valve deeper, which has proven to cause serious difficulties in the behavior of cams and springs. SUMMARY OF THE INVENTION The present invention, unlike the prior art, varies the valve overlap or timing in a conventional camshaft or a double effect distribution sequential valve shaft. The device of the present invention, unlike the prior art, also allows the valve overlap or timing and the opening section to be varied in a double effect distribution sequential valve shaft. The present invention includes an automatic valve overlap or timing and valve section variator or an automatic valve overlap or timing variator for use in internal combustion engines and machines which use valve-type distribution systems with cams or distribution valve shafts. The invention includes an automatic mechanism controlled by a microprocessor which is activated by a signal received from a tachometer, or gas analyzer, or both. The automatic mechanism activates a motor reducer with a step motor or a servo motor which turns a number of predetermined turns or steps. The motor reducer, by means of a hollow and internally threaded crown of the reducer, causes an end of a spindle to advance against bearings which push the SVS shaft or a conventional camshaft against a dragging pulley by means of a multiple entrance grooved screw etched in at one end of the shaft and an threaded sleeve inside the pulley in such a way that a differential and controlled turn is produced in the SVS or conventional camshaft with respect to a dragging pulley. As a result the position of the SVS or conventional camshaft is changed angularly with respect to the other shaft. The valve overlap or timing is thereby varied while the engine is turning. The rotation which changes the angular position of the SVS shaft is concurrent with a longitudinal displacement of the shaft, both resulting from the action of the spindle against the end of the shaft. Such displacement will change the relative positions of the perforations or openings in the shaft and in the jacket in which the shaft is inserted, whereby their common area will be less than if they coincided entirely. The variation in valve area may occur in either sense, i.e. the common valve area may be increased or decreased. The step motor or servo motor can be actuated in forward or reverse with the effect of changing simultaneously the overlap and the valve section conditions of the distribution system. Such effect is obtained by the coordinated variation of both SVS shafts, one for intake and one for exhaust. BRIEF DESCRIPTION OF THE DRAWINGS The illustrations referred to below describe a variator for use in a single SVS or a conventional camshaft. Fig. 1A illustrates the distribution system with which the present invention is used. Fig. 1B illustrates a detailed view of a portion of the distribution system in Fig. 1A. Fig. 2A illustrates a top elevation view of the variator of the present invention Fig. 2B illustrates a cross-sectional side elevation view of the variator of Fig. 1A taken along the line A-A. Fig. 3 illustrates the mounting of the system of the present invention on the distribution system illustrated in Fig. 1A in a frontal view. Fig. 4 illustrates the mounting of the system of the present invention in a lateral view. Fig. 5 illustrates the mounting of the system of the present invention in a superior view. Fig. 6A illustrates a diagrammatic view of a conventional camshaft and valve arrangement used with the variator of the present invention. Fig. 6B illustrates a cross-sectional side elevation view of the variator used with a camshaft distribution system. DETAILED DESCRIPTION The present invention is described below by illustrating its function as it relates to a system in an engine with a double effect distribution sequential valve shaft system ("SVS"), as shown in Figs. 1A and 1B, located in the cylinder head of the engine and driven by toothed pulleys and belts, gears, or chains with one shaft for intake and another for exhaust. The present invention may, however, be used with a conventional camshaft such as a double overhead camshaft with poppet valves, or other distribution system. The SVS shafts include two longitudinal shafts (a) and (b) on the cylinder head 5 aligned with the engine axis, comprising a jacket 1 and a shaft formed with holes, i.e., a holed shaft. The engine includes motor block 7, piston 8, cylinder head 5, connecting rod 12, a distribution toothed belt 9, distribution and reduction toothed pulley 11, tension pulley 13, and motion distribution toothed pulley 14. Since both shafts (a) and (b) (intake and exhaust) are practically identical, only one of them will be described. A housing for two jackets is provided in the cylinder head cover 5, with outer water chambers. The jacket 1, with perforations or openings 20 from side to side in the vertical plane of the jacket, is inserted into the housing under pressure and with a sealer. Each opening 20 coincides with a combustion chamber of each cylinder of the engine. A double effect distribution sequential valve shaft 2 is mounted inside the jacket 1 with a very accurate tolerance. The shaft also has perforations or openings 22 extending from side to side in the vertical plane. Each opening 22 is separated from the other by the same distance between cylinders and is placed at a predetermined angle in the vertical plane, depending on the sequence of intake or exhaust on the type of engine. Because the openings 22 of the shaft are side to side in the vertical plane, at every complete turn, one of the openings 22 communicates twice every turn through an opening 20 in the jacket 1 with a hole 24 in the head of one combustion chamber of a given cylinder 3, for which reason it is named "double effect." Thus, one complete turn of the crankshaft need only result in 1/4 of a turn of the double effect distribution sequential valve shaft 2. The rotation of the valve shaft is transmitted from a pulley 14 on the crankshaft 25 by means of pulleys and toothed belts 11 and 9, with a corresponding difference of diameters to reduce the number of turns to 4:1. The exhaust or intake exit is shown at 4 in Fig. 1B. The present invention is described below according to details of Figs. 2A, 2B, 3, 4 and 5. The present invention is an automatic mechanism commanded by an electric motor embodied as a servo-motor or a step motor whose turns are controlled by an electronic circuit. The electronic circuit receives instructions from a tachometer, gas analyzer, or both, which indicates the variations of valve overlap or timing for a certain rate of revolutions per minute. As shown in Figs. 2A and 2B, a motor reducer 42 forms a single body with a worm gear and an endless worm or screw. A holder plate of the motor reducer 42 is coupled to a motor body 37 by means of screws 43. The shaft 2 has at its end a grooved trapezoidal screw channel 41 with multiple entrances which is screwed into a hollow and threaded sleeve 34 which is engaged with a toothed pulley 49 by means of a pin. The threaded sleeve 34 is restrained from moving longitudinally by means of a seeger ring 35. A plate 27 supports the whole unit and is fixed to the block by means of screws 38. The plate 27 supports a ball bearing 30 which is fixed in its position with the seeger ring 35 and rubber locks 28 and 29. The toothed pulley 49 and the threaded sleeve 34 are fixed to the ball bearing 30 by means of a ring 31 and screws 33 such that longitudinal movement of the pulley is restrained and the pulley is only able to turn. The SVS shaft 2 has etched on its end a housing for axial ball bearings 40. A cap with screws 45 and a rubber lock 46 close the housing. A pushing spindle 44 is retained between both axial ball bearings 40. The pushing spindle 44 in turn is screwed into the hollow bore of the worm gear of the motor reducer 42. The spindle 44 has a longitudinal square section groove in which a pin 39 enters, in such a way as to prevent the spindle 44 from turning while allowing longitudinal movement. The pin 39 is fixed to the body 37 by means of a screw 32. When the motor reducer 42 receives a signal, it moves a determined amount of turns or steps. The rotation of the motor reducer 42 is transmitted to the spindle 44 which pushes the shaft 2 along the grooves 41. The shaft 2 thereby turns over itself according to the produced advance. When the motor reducer 42 completes its rotation, the whole unit has produced a differential rotation resulting in advance of the shaft 2 and amplification or reduction of the common area between the shaft perforations or openings 22 and those of its jackets. The rotation of the shaft 2 also changes the valve overlap with respect to the other twin shaft, and with reference to the position of the piston at the top or bottom of its motion. As shown in Fig. 5, the opening for the intake or the exhaust of the mixture or the gases through the cylinder head covers has been indicated at 24 and the opening on the shaft has been indicated at 22. When one shaft is cross turned in respect to the jacket, the opening 22 has been advanced relative to the opening 24. In order to simplify the description, the projections of the openings in Fig. 5 have been indicated without taking into account the turning of the shaft 2. After the shaft 2 is advanced relative to the jacket, the effective opening is determined by the common area between the opening 24 and the opening 22. The maximum possible opening will be area of opening X. The variation of the valve overlap and the valve section is carried out while the engine is running and at any range of revolutions per minute. The whole system is protected by a box or housing 36 fixed to the plate 27 by means of the screws 38. A removable cap 47 allows for the change of a distribution belt whose possible positions are indicated at 48. Fig. 3 shows the mounting of the system in a frontal view, while the mounting of the system laterally is shown in Fig. 4. Fig. 5 shows the top view of the assembly shown in Fig. 4. In its application to a conventional camshaft, the variator of the present invention is used with a camshaft which is able to move axially a certain distance. The camshaft has the grooved screw channel 41 with multiple entrances etched at its end and a housing for axial ball bearings 40. The cap 45 and rubber lock 46 close the housing. The spindle 44 pushes the camshaft along the grooves 41 thereby moving the camshaft axially and in rotation. The distance of the movement in rotation of the camshaft depends on the pitch of the screw with multiple entrances 41. The axial movement of the camshaft occurs concurrently with the rotation of the camshaft thereby changing the angular position of the camshaft. As a result, the relative position of the cams in respect to the valve rod or rocker arm is different from what it was at the top dead end of the piston. The timing of the valve has thereby been changed and a new overlap has been achieved. Further, it should be noted that in order to facilitate axial movement of the camshaft the cams may be broadened. The device of the present invention may be moved directly by a separate reducer, by a single body motor reducer of the type having a worm gear or crown and endless worm or screw or by other known type. The screw threads may be of any known type. The threaded sleeve 34 and shaft 2 may have one or multiple entrances of any pitch. In other words, if the pitch were infinite there should be a groove of parallel teeth so that when the spindle 44 pushes the shaft 2 there is only longitudinal movement, without rotation, thereby varying only the valve section in the system. The threaded sleeve 34 may be a separate element or form one single body with the pulley. The pulley and the spindle 44 may be mounted on bushings or bearings of any type. Lubrication may be in an independent circuit or, depending on the engine, or may be provided by auto-lubricating mechanisms. The invention may be commanded by an electronic or electric circuit, with input of one or more variables or combinations thereof. Further, the invention may be set up with a sensor in such a way that when the main engine stops, the valve overlap position and the valve section return to the position at the point of start up. The present invention advantageously allows the optimum performance of intake or exhaust of gases at any rate of revolutions per minute, to be obtained automatically. As a result, the present invention allows: (a) greater efficiency in expulsion of exhaust gases; (b) greater efficiency of mixture intake; (c) better combustion in the chambers; (d) greater power generation at a given rate of revolutions per minute; and (e) less combustion residuals due to a better burning of the fuel mixture.

Claims: An automatic variator assembly for varying the valve timing in a valvular distribution system in an internal combustion engine which includes an engine block (7), a cylinder formed in the engine block, the cylinder having a cylinder head (5), a piston (8) slidable within the cylinder, and a combustion chamber bounded by the cylinder and the piston (8), and a distribution system consisting of two camshafts (2) with valves located in the cylinder head (5), the variator assembly comprising: an automatic mechanism; a spindle (44) for moving one of said camshafts (2), an electric motor (42) activated by said automatic mechanism which causes an end of said spindle (44) to advance and push the camshaft (2) forward or pull it back and a threaded sleeve (34) characterized in that the automatic mechanism is controlled by a microprocessor; the electric motor (42) turns a number of predetermined turns or steps for causing an end of said spindle (44) to advance and push the camshaft (2) forward or pull it back: a multiple entrance grooved screw (41) is etched in at one end of said camshaft (2), turning inside said threaded sleeve (34), in such a way that a differential and controlled turn is produced in said camshaft (2) whensaid spindle (44) moves said camshaft (2), causing a rotation of said camshaft (2) and longitudinal displacement of said camshaft (2), thereby varying the valve timing while the engine is turning. The variator assembly according to claim 1, wherein said automatic mechanism is activated by a signal from a tachometer and gas analyzer. The variator assembly according to claim 1, wherein said threaded sleeve (34) is fixed relative to and inside of a toothed pulley (49) by means of a pin. The variator assembly according to claim 1, wherein said motor is a motor reducer (42) having a worm gear and said spindle (44) is screwed into said worm gear. The variator assembly according to claim 1, wherein said electric motor is a step motor. The variator assembly according to claim 1, wherein said electric motor is a servo motor.

Inventors: SCHIATTINO MILJENKO, SCHIATTINO, MILJENKO
Applicants: SCHIATTINO MILJENKO, SCHIATTINO, MILJENKO
Application year: 1994
Main classification: F01L1
IPC codes: F01L7, F01L1, F02F7